Immunohematology

Immunohematology

the use of techniques and procedures to study the immune system’s response to ‘allogenic’ blood cells

Allogenic

tissues, cells, or organs are transferred between genetically different individuals of the same species

Antigen

any molecule or molecular structure that can specifically bind to an antibody or an immune receptor, triggering an immune response

Immunogen

an antigen that can actively trigger an adaptive immune response by activating B or T cells

Antigenicity

ability to be specifically recognized and bound by immune molecules

(antibodies and T cell receptors) (passive)

Immunogenicity

ability to induce and trigger an actual immune response leading to immunity or immune activation, (an active term)

Antibodies

protein found in plasma and in other body fluids

When are antibodies produced?

as a result of antigen stimulation

When are immunoglobulin (Ig) class of antibodies stimulated?

By RBC antigens

What are some immunoglobulin (Ig) class of antibodies?

IgM, IgG and IgA

What does it mean if the antibody response is usually polyclonal?

Many clones are made

What is the nature of antigen-antibody binding?

Binding is reversible

What is the equation for the association constant of antibodies?

Ka = [AgAb] / [Ag][Ab]

What are the variables in the association constant of the reaction?

Ag = Antigen, Ab = Antibody, and Ka = binding equilibrium or the association constant of the reaction

What does the the dissociation constant measure?

the strength of antibody binding, a.k.a., antibody affinity for the antigen

What is the equation for the dissociation constant?

Kd = [Ag][Ab] / [AgAb]

What does Kd measure?

the strength of the bond (non-covalent) between the Ag and Ab

What is the structural precursor for A and B antigens?

The H antigen (contains L-fucose).

What sugar is added to the H antigen to form the A antigen?

N-acetyl-D-galactosamine (GalNAc)

What sugar is added to the H antigen to form the B antigen?

D-galactose (Gal).

What does Type O blood have in terms of ABO antigens?

Only the H antigen—no additional immunodominant sugar.

Why is Type AB considered the universal recipient for RBCs?

It has both A and B antigens, so the plasma contains neither anti-A nor anti-B antibodies.

Where are the ABO antigens located chemically?

On glycolipids and glycoproteins on the RBC surface.

What is forward typing?

antisera are used to detect the specific RBC antigen

Group O individuals had agglutination to what?

No agglutination

Group A individuals had agglutination to what?

Anti-A serum

Group B individuals had agglutination to what?

Anti-B serum

Group AB individuals had agglutination to what?

Anti-A and Anti-B serum

What is the dominance of The Group A and B genes?

co-dominant

What is the the immunodominant sugar in the A antigen?

N-acetyl-D-galactosamine

What is the the immunodominant sugar in the B antigen?

D-galactose

What is the the immunodominant sugar in the O or H antigen?

L-fucose

What is Rh(D) immune globulin (RhIG)?

A medication composed of anti-D IgG antibodies derived from human plasma

What is the most immunogenic and clinically important Rh antigen?

The D antigen

Why is the D antigen clinically important?

It is involved in most Rh-related transfusion reactions and hemolytic disease of the fetus and newborn (HDFN)

What conditions are commonly caused by antibodies to the D antigen?

Rh transfusion reactions and hemolytic disease of the fetus and newborn (HDFN)

What does the D antigen represent in the Rh system?

Presence of the D antigen (Rh positive)

What does “d” mean in the Rh system?

Absence of the D antigen (there is no actual d antigen)

What are the main antigens of the Rh system named by Fisher and Race?

D, C, c, E, e

What does the lowercase c indicate in the Rh system?

Presence of the c antigen

What does the lowercase e indicate in the Rh system?

Presence of the e antigen

Which Rh antigen is most likely to cause HDFN?

The D antigen

Where are Rh (D) Antibodies?

IgG immunoglobulin

What is an Allogeneic transfusion or donation?

a donor and a recipient are not the same person

How is the D antigen expressed?

Co-dominantly

what happens if the baby is Rh positive and the mother is Rh negative?

Rh-negative mom + Rh-positive baby → risk of HDFN in later pregnancies → prevented with RhIg given during and after pregnancy.